Studies from this laboratory indicated that in fasted rats branched chain amino acids are required for the in vivo stimulation of initiation of protein synthesis by insulin in muscles. This was determined by measuring the ratios of polysomes/subunits in extracts of psoas muscles. We plan to determine whether or not this effect is specific for branched chain amino acids, whether the three branched chain amino acids are equally effective and whether or not the effect can be obtained with branched chain alpha-keto acids. Studies concerning the effect of diabetes, insulin, other hormones and substrates on protein synthesis and protein degradation in different types of muscles will be continued, as well as studies concerning the regulation of amino acid metabolism and release by muscle. The precursor(s) of the carbon skeleton of alanine will be investigated in control and diabetic muscles, and factors which regulate the de novo synthesis and release of alanine, glutamate, glutamine and ammonia from skeletal muscle in control, fasted and diabetic animals. Efforts to solubilize the mitochondrial enzyme which catalyses the oxidative decarboxylation of the branched chain alpha-keto acids will be continued; studies of its structure and regulation will be attempted. BIBLIOGRAPHIC REFERENCES: Buse, M.G., Herlong, H.F. and Weigand, D.A. The effect of diabetes, insulin and the redox potential on leucine metabolism by isolated rat hemidiaphragms. Endocrinolgoy 98:1166, 1976. Buse, M.G., Herlong, H.F., Weigand, D.A., and Spicer, S.C. The effect of diabetes, insulin and Wallerian degeneration on leucine metabolism of isolated rat sciatic nervers. J. Neurochem. 27: 1339, 1976.